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. 2017 Dec 14;9(5):6015–6027. doi: 10.18632/oncotarget.23210

Figure 7. E7 expression by KC alters hierarchy of killing mechanisms used by CTL.

Figure 7

Putative differences in the hierarchy of killing mechanisms used by CTL to kill KC expressing E7 compared with non-transgenic B6KC targets as modeled by in vitro killing studies in this study. Cytokines inhibitory to a specific killing mode are indicated by dotted lines. Without oncogene expression, B6KC were killed predominantly by perforin and TNFα mediated mechanisms, both of which were essential, while Fas/FasL and IFNγ were less important modes of killing. PD-L1 is not expressed in B6KC, and blockade had no effect on killing, and this has been excluded from the diagram. With expression of E7 oncogene, E7KC still require TNFα as essential for killing. Less significantly, IFNγ and perforin contribute to killing targets. IFNγ-independent killing does take place, but it appears not to be mediated by any of the processes we examined here. Perforin-independent killing is reliant on Fas/FasL or on IFNγ. PD1/L1 contributes to target cell death perforin-independent killing, but along with Fas/FasL, inhibits killing by IFNγ and perforin in perforin-sufficient T cells.